I thought you just had to make make sure that there is nothing on the seat ,and the function just zeros out the sensor, but maybe the newer air bags can deploy the bag at a lower force for a lighter seat occupant and this function has evolved to multiple steps requiring adding specific weights. Just don't have the wife sit there if it calls for only a 100 lbs. or you might end up launching your kid out the back door like a Howitzer went off :-)